If they are aquarium fish, most LFS will take them in for free every time (why not, they get free product to sell)
If they are rare in the sense that they are hard to find, and are decent to keep in tanks, I would try to sell them here in the marketplace, or on craigslist.
If they are natives or undesirable species for an aquarium, you might have to make some fish tacos
If they are rare in the sense that they are hard to find, and are decent to keep in tanks, I would try to sell them here in the marketplace, or on craigslist.
If they are natives or undesirable species for an aquarium, you might have to make some fish tacos